Wireless Home Automation Networks: A Survey of Architectures and Technologies

Carles Gomez and Josep Paradells

Presented by Deepen Solanki and Aishwarya Rao

Table of Contents

1. Introduction to WHANs2. Solutions for WHANs

a. ZIGBEEb. Z - WAVEc. WAVENISd. INSTEONe. IP BASED

3. Discussion4. Conclusion

INTRODUCTION - WHANs

● Remote Control of Devices - Appliances● Remote Care - wearables, fall detection ● Smart Energy Monitoring - HVAC, usage patterns● Security Systems - burglar alarm, smoke detection

Sensors Actuators

Monitoring Control

Connectivity

WHAN

Characteristics

● High node density - (100s) ● Multipath environment - multiple reflective surfaces ● Interference - Bluetooth devices, microwave ovens● Multihop communications - combating range● Self-healing network - mobile devices● Various traffic patterns - P2P, P2MP, MP2P● Quick results - emergency situations● Internet connectivity - Remote monitoring ● Highly constrained nodes - memory, processing power

INTRODUCTION - WHANs

● ZigBee● Z-Wave● INSTEON● Wavenis● IP Based Solutions

SOLUTIONS FOR WHANs

ZIGBEE (2004)● Low Data Rate - 20, 40, 250kbps ● Short Range - 10 to 100m ● Bands - 868MHz / 915MHZ / 2.4GHz● DSSS

● Channel access Beacon

Beaconless

● Device types Coordinator

RouterEnd device

● Tree, Mesh ZigBee Home Automation Public Application Profile

● Profiles

ZigBee Smart Energy Profile

● Reliable transmission of short messages from a control unit to one or more nodes in the network

● 868.42 MHz in Europe, 908.42 MHz in US, 2.4GHz*● Low data rate - 9.6kb/s, 40kb/s, 200kb/s*● MAC Layer - CSMA/CA● Source-routed mesh network● Range - 90m outdoor, 20m indoor

Z-WAVE (1999)

● Device types

Controller End device

● primary / secondary● initiations, retransmissions● routing tables ● exclusions, node IDs

● blindly execute commands ● routing slaves and static tables

WAVENIS● Low-power, long-distance wireless communications● Data rates between 4.8kb/s and 100kb/s● 433MHz, 868MHz, 915MHz, 2.4GHz

● MAC LayerSynchronous

Non - synchronous

CSMA/TDMA

CSMA/CA

● Only one type of device, virtual tree hierarchy

http://www-coronis-com.dyn.elster.com/downloads/Wavenis_Data_Sheet_A4_CS5.pdf

New device → Broadcast request → QoS → Joined!

● Dual mesh topology● Links between devices can be either RF lines, power lines or both● FSK, 904MHz, 38.4kb/s● All devices are peers● Not in range? → time-synchronized multihop● Simulcast → devices within same range can transmit messages simultaneously

INSTEON (2005)

IP-BASED SOLUTIONS● IPSO Alliance● IPv6 over Low power Wireless Personal Area Networks → 6LoWPAN● Fragmentation, Header compression, address auto-configuration, neighbor discovery● Organization

○ Edge router = the bridge○ Mesh router○ Nodes

http://www.ti.com/lit/wp/swry013/swry013.pdf

IP-BASED SOLUTIONS

http://www.ti.com/lit/wp/swry013/swry013.pdf

DISCUSSION

Physical Layer

Modulation and Spread-Spectrum Techniques

● FSK- easy to implement, used by Z-Wave and INSTEON● GFSK- greater spectral efficiency than FSK, used by Wavenis ● PSK- More complex but better SNR, used by ZigBee● Spread Spectrum techniques provide protection against multipath and narrowband interference-

ZigBee and Wavenis

Single Channel vs. Multichannel

● ZigBee coordinator can decide to re-form the whole network in a new channel if severe interference is detected by any node

● Single channel sub gigahertz operation exploits lower susceptibility to interference than 2.4GHz band to simplify hardware design

DISCUSSION

Link Layer

Reliability:

● Z-wave and INSTEON use 8-bit checksum● ZigBee and 6LoWPAN use 16-bit checksum● Optional link layer ACKs for reliable link transmission

Delay:

● For reliable mode, the roundtrip time including transmission of an ACK is provided● 900 MHz channels

DISCUSSION

Network Layer

Routing/Multihopping State

● Z-Wave- only the controller stores and maintains a routing table ● ZigBee- recommends the use of large routing tables due to high density expected in a residential

scenario, which increases memory requirements on nodes● Wavenis- each device only stores its own route to the root, root stores the routes to reach each

node● INSTEON- use simulcast instead of routing, avoids the need to store state for multihop

communications

DISCUSSION

Routing Metrics

● ZigBee and 6LoWPAN use link quality indicator (LQI) offered by IEEE 802.15.4● Wavenis uses a link quality estimator based on RSSI- may not be accurate due to interference and

multipath

Route Change Latency

● INSTEON uses simulcast instead of routing so doesn't suffer from a connectivity gap● Other solutions experience the latency for detecting the link failure and finding an alternative path ● 1s for Z-wave, 50-100ms for ZigBee

DISCUSSION

End to End Reliability

● ZigBee filters duplicate packets● In 6LoWPAN, use UDP augmented with sequence numbers, ACKs, and retries

Application Layer

● ZigBee, Z-Wave, and INSTEON - well defined commands and attributes for various WHAN applications

DISCUSSION

Security

● ZigBee, Z-Wave 400 series, Wavenis and 6LoWPAN- 128-bit key Advanced Encryption Standard (AES) algorithm

● INSTEON offers various encryption methods but recommends the use of simple rolling-code encryption

Internet Connectivity

● 6LoWPAN is intrinsically interoperable with the Internet- avoids issues in terms of security, management, and consistency in QoS policies

DISCUSSION

Implementation Size

● ZigBee, Z-Wave, and INSTEON implement protocol architectures up to application-layer functionality

● Zigbee requires largest footprint, INSTEON requires least memory● Wavenis consumes a small amount of RAM but requires a medium flash memory size● 6LoWPAN implementations require less ROM/flash than ZigBee, Z-Wave, and Wavenis

Standardization and Market Adoption

● 6LoWPAN unlike the others is open, and its implementation does not require a license● ZigBee products in the market has been delayed in comparison with those based on other solutions● Smart Energy Version 2 - providing end-to-end connectivity between energy providers and

consumers

DISCUSSION

CONCLUSION

● ZigBee and 6LoWPAN were designed for general purposes● Other solutions were developed for specific application● Trend in converging toward IP- future WHAN applications will benefit from

enhanced quality, security, and interoperability.

Questions?